Dermestes haemorrhoidalis Küster, 1852
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POLYPHAGA Emery, 1886
BOSTRICHOIDEA Latreille, 1802
DERMESTINAE Latreille, 1804
Dermestes Linnaeus, 1758
Dermestes Linnaeus, 1758
Native to the Palaearctic region and found sporadically throughout Europe, this species now occurs regularly throughout the world although it is rarely established outside artificial conditions; under such circumstance it occurs from the Mediterranean to the very north of Fennoscandia and during the warmer months can become temporarily established outside. In the UK it occurs regularly in domestic and commercial food storage areas and large and persistent populations can be common but records from the wild, where they can breed among avian nesting material or carrion, are rare and mostly scattered across the south. Under artificial conditions the species may be continuously brooded and life stages may occur year-round, adults become active during longer and warmer days, generally from April until October or November, they are crepuscular and nocturnal and disperse on warm evenings, often being attracted to light and entering windows during the summer. Once inside buildings they tend to settle on walls or ceilings and remain still for a while until specimens of the opposite sex arrive, mating usually occurs soon afterwards and females fly or crawl away to find suitable oviposition sites. Adults rarely feed although in warmer climates they frequently visit flowers and have been observed consuming nectar and pollen. Females are fecund and under good conditions the life cycle is rapid and so large populations can build up under unhygienic conditions; females live for about five months, during which time they oviposit regularly after mating and produce up to 180 eggs over their lifetime, oviposition being more frequent when they have access to moisture. Eggs are laid in batches in crevices or among a wide range of host materials and while they have been recorded from e.g. stored sausages and bacon, they generally prefer dry products such as dried meats and fish, pasta, egg noodles and may attack leather, hair, natural fibres and feathers if need be, this versatility is an extension of their wild behaviour where they are thought to be mostly saprophagous among decaying wood or avian and hymenopteran nests. Larvae develop rapidly, they pass through at least
five instars but this may increase under unfavourable conditions and, depending on host material and temperature etc, may be fully grown within five weeks, at this time they bore into any convenient substrate to form a pupal chamber, this is often packaging material but they have also been recorded boring into books, polystyrene tiles and even electrical cables. Larvae are typical of the family and so very distinctive; they have a well-sclerotized head, short but robust legs, are dark brown or grey with conspicuous paler bands and long pubescence and the dorsal surface of the terminal abdominal segment has two long tubercles which may be hidden among the pubescence. Unlike larvae of some other genera within the family, they are rarely seen away from the host material except when they wander off to pupate, but they tend to occur in numbers and their presence soon becomes obvious among stored food etc. Development can occur over a wide range of conditions and they can withstand periods of cold and drought, conditions vary with members of the genus but in the present case ideal conditions are 75% r.h. and 27-30°C and development stops above 40°C. Dermestid larvae destroy food by consuming it directly and also leaving frass and moulted skins behind, they are also known to introduce or disperse fungi and infection through host material, where food is stored in large quantities and infestation may develop very quickly as larvae are mobile and fresh adults tend to infest new material.
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One of several all-dark UK species, adults need to be identified by examining several underside characters. Dorsal surface dark brown, sometimes almost black, legs paler brown and antennae pale reddish-brown, underside dark brown with fine recumbent pale brown hairs throughout (without any pattern) through which the cuticle is plainly visible. Two characters are important in identifying this species; the basal abdominal sternite has almost straight lines before the lateral margin (in D. ater they are strongly incurved), and the elytral have dense pubescence which clearly extends beyond the apical margin (in D. peruvianus it is shorter and is at most barely visible beyond the margin. Head hypognathous with large convex eyes and short antennae bearing an abrupt elongate and 3-segmented club. Pronotum transverse, broadest in front of rounded posterior angles and curved to a narrow apical margin, the anterior angles hardly suggested from above, basal margin strongly sinuate, surface evenly convex, finely punctured and pubescent throughout and with variable but usually weak basal fovea. Elytra finely punctured throughout and without striae, smoothly convex but usually with one or two weak longitudinal ridges which are sometimes visible only under the shoulders, pubescence dark reddish-brown or black with yellow hairs fairly regularly scattered throughout. Males have a small median tubercle before the apical margin of the fourth abdominal sternite; in females this sternite is smooth.